As known, many pourable food products, such as fruit juice, UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are sold in containers made of sterilized sheet packaging material.
A typical example of this type of containers is the parallelepiped-shaped container for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material.
The packaging material has a multilayer structure substantially comprising a base layer for stiffness and strength, which may include a layer of fibrous material, e.g. paper, or mineral-filled polypropylene material, and a number of lamination layers of heat-sealable plastic material, e.g. polyethylene films, covering both sides of the base layer.
In the case of aseptic containers for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH) film, which is superimposed on a layer of heat-sealable plastic material, and is in turn covered with another layer of heat-sealable plastic material forming the inner face of the container eventually contacting the food product.
Containers of this sort are normally produced on fully automatic packaging machines, which are fed with a web of packaging material that is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution, which, once sterilization is completed, is removed from the surfaces of the packaging material, e.g. evaporated by heating. The web of packaging material so sterilized is then maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is filled with a sterilized or sterile-processed food product, and is sealed and subsequently cut along equally spaced cross sections to form pillow packs, which are then folded mechanically to form respective finished, e.g. substantially parallelepiped-shaped, containers.
Alternatively, the packaging material may be cut into blanks, which are formed into containers on forming spindles, and the containers are filled with the food product and sealed. One example of this type of container is the so-called “gable-top” container known by the trade name Tetra Rex (registered trademark).
To open the containers described above, various solutions have been proposed, including reclosable opening devices made of plastic material and substantially comprising a pouring spout, defining a through pouring opening and fitted to a hole in a wall of the container.
When producing the opening device, the opening of the pouring spout is sealed by a closing element connected integrally to the pouring spout and detachable from it along a tear line. The closing element extends at the same level as the packaging material, so as to seal the hole in the wall of the container. On the side facing the lid, the closing element has an integral projecting pull ring, the free end of which is pulled by the user to detach the closing element from the pouring spout along the tear line and so open the pouring opening. More specifically, the pull ring extends inside, and at a predetermined distance from, the pouring spout.
It is also possible to fix the closing element of the opening device directly over a prelaminated hole in the packaging material, i.e. a hole formed in the base layer only and covered by the other lamination layers, including the layer of gas-barrier material.
In both cases, a removable, e.g. a screw lid, is subsequently fitted to the pouring spout in order to outwardly close the latter.
EP2886479 discloses an opening device having a closing element that is formed in one piece with a protruding portion extending inside the pouring spout and welded to the lid. The latter is provided with a disk-shaped welding promoting element that is welded to the protruding portion so that, when removing the lid from the pouring spout, the protruding portion and the closing element remain attached to the lid.
The welding promoting element has to be fixedly connected to the lid and to the protruding portion in order to allow a one-step-opening of the opening device, i.e. to assure that the closing element remains attached to the lid, through the protruding portion, when the lid is removed from the spout for the first time.
Therefore, the need is felt for a strong connection between the welding promoting element, the lid and the closing element.